Method for recovering materials from waste tires

ABSTRACT

A waste tire processing apparatus ( 10 ) reacts waste tires ( 26 ) with a molten reactant metal ( 19 ) to recover primarily carbon and stainless steel. The apparatus ( 10 ) includes a tire positioning arrangement ( 20 ) for positioning the waste tires ( 26 ) in the molten reactant metal ( 19 ) for a reaction period. After the reaction period, the tire positioning arrangement ( 20 ) removes from the molten metal non-reacted solids remaining after the reaction. The non-reacted solids comprise primarily stainless-steel included in the waste tires. As the waste tires ( 26 ) are reacted in the molten reactant metal ( 19 ), a gas recovery arrangement ( 14 ) collects process gases released from the molten metal. The gas recovery arrangement ( 14 ) recovers primarily carbon, metal salts, hydrogen, and nitrogen.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application is a divisional of U.S. patentapplication Ser. No. 09/154,636, filed Sep. 17, 1998, entitled “METHODFOR RECOVERING MATERIALS FROM WASTE TIRES,” now U.S. Pat. No. ______.The Applicants claim priority from this parent application under 35U.S.C. §120. The disclosure of the parent application is incorporatedherein by this reference.

TECHNICAL FIELD OF THE INVENTION

[0002] This invention relates to recycling materials made up of organiccompounds and metals such as stainless-steel. More particularly, thisinvention is directed to an apparatus and method for processing wastetires to recover primarily carbon and stainless-steel.

BACKGROUND OF THE INVENTION

[0003] Used vehicle tires pose a significant environmental threat. Evenwith sufficient landfill space, whole tires are too flexible to beplaced in landfills. Storing waste tires above surface is unacceptablebecause whole tires not only take up a great deal of space, but alsocreate habitat for insect pests and rodents. Waste tires may beincinerated but the combustion process releases massive amounts ofpollutants into the atmosphere unless expensive scrubbing systems areused to clean incinerator exhaust gases. Incineration also leaves ashwhich must be disposed of in some manner. Also, waste tires must beshredded or otherwise comminuted into small pieces in order to burnefficiently in an incinerator.

SUMMARY OF THE INVENTION

[0004] It is a broad object of the invention to provide an apparatus andmethod which overcome the above-described the problems and othersassociated with the disposal of waste tires. Another object of theinvention is to provide a waste tire treatment apparatus and processwhich recovers useful materials from the tires.

[0005] The method of recovering material from waste tires according tothe invention includes reacting substantially whole waste tires with amolten reactant metal. The waste tires react with the molten metal toproduce primarily carbon gas and metal salts in molten or gaseous form.After a reaction period during which time the waste tires are in contactwith the reactant metal, the method includes removing non-reacted solidsfrom the reactant metal. These non-reacted solids comprise mainlystainless-steel which was included in the tires. Removing anystainless-steel remaining after the reaction period prevents thestainless-steel from dissolving into the reactant metal and corruptingthe reactant metal bath.

[0006] Importantly, the tire treatment method according to the inventiondoes not require shredding or otherwise comminuting tires into smallpieces, and therefore eliminates the expense associated with thisprocessing step. Also, the present waste tire treatment method releasesonly hydrogen gas and perhaps nitrogen gas to the atmosphere.Substantially all carbon from compounds which make up the tires isrecovered as pure elemental carbon. Other elements included in compoundswhich make up the tires are recovered as metal salts. Stainless steelrecovered in the process may be reused.

[0007] The apparatus for performing the tire treatment method accordingto the invention includes a reactor vessel which may be charged with asuitable reactant metal, preferably including mostly aluminum. A heaterassociated with the reactor vessel heats the reactant metal to a moltenstate and a circulating system preferably associated with the reactorvessel and heater circulates fresh reactant metal into the reactorvessel. The apparatus also includes a tire positioning arrangement and agas recovery arrangement.

[0008] At least one and preferably several tire carriers are included inthe tire positioning arrangement. Each tire carrier comprises astructure on which waste tires may be loaded and then lowered into themolten reactant metal in the reactor vessel. Each tire carrierpreferably includes an open support structure which allows the moltenreactant metal to flow through the structure and around the waste tiresas the carrier structure and tires are lowered into the reactant metal.

[0009] A carrier lift structure is associated with each tire carrier formoving each tire carrier between a loading/collecting position away fromthe reactor vessel and a reaction position within the reactor vessel.The tire lift structure includes an arrangement for moving each tirecarrier vertically so that each carrier may be lowered into the reactorvessel and lifted from the reactor vessel. The tire lift structure isalso capable of moving each tire carrier laterally away from the reactorvessel to the loading/collecting position. A cooling system may beassociated with the tire lift structure for cooling each carrier and anynon-reacted solids remaining after removal from the molten reactantmetal.

[0010] The tire positioning arrangement also includes a tire submergingsystem including a tire contactor member and a contactor actuator. Asthe waste tires are lowered into the reactant metal on a tire carrier,the tires may tend to float on the surface of the molten reactant metalrather than sink below the surface. The tire contactor member is inposition to move downwardly over the waste tires, pushing the tires intothe molten reactant metal and holding the tires beneath the surface ofthe reactant metal for the reaction period.

[0011] The gas recovery arrangement includes a gas recovery hood whichis placed in an operating position over the waste tires and tire carrierbefore the tires are submerged into the molten reactant metal. In theoperating position, the lower edge of the hood extends below the surfaceof the molten reactant metal to form a seal with the surface of thereactant metal around the area in which the tires are to be submerged.Once the gas recovery hood is in the operating position, and preferablypurged of air with a suitable inert gas, the tire carrier and loadedwaste tires are lowered into the reactant metal.

[0012] The gas recovery hood collects process gases released from thesurface of the molten reactant metal. The process gases includeprimarily gaseous carbon and gaseous metal salts along with hydrogen andperhaps nitrogen. The collected process gases are passed through anaqueous scrubber to cool and remove the carbon and metal salts. Asuitable liquid/solid separator separates the solidified carbon from thescrubber effluent and the remaining solution is then treated by asuitable process to remove the metal salts.

[0013] The waste tire treatment apparatus and method of the inventionquickly recovers carbon and stainless steel from substantially wholeused tire carcasses. Both the carbon and stainless steel may be reusedin various products. Also, the apparatus and method producesubstantially no harmful gaseous emissions.

[0014] These and other objects, advantages, and features of theinvention will be apparent from the following description of thepreferred embodiments, considered along with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1 is a diagrammatic representation of a waste tire processingsystem embodying the principles of invention.

[0016]FIG. 2 is a somewhat diagrammatic side view of an apparatusembodying the principles of the invention for processing waste tires.

[0017]FIG. 3A is a mostly diagrammatic representation of a tire carrierand gas recovery hood in a ready position.

[0018]FIG. 3B is a diagrammatic representation similar to FIG. 3A butwith the hood in the operating position.

[0019]FIG. 3C is a diagrammatic representation similar to FIG. 3B butwith the tire carrier in the reaction position submerged below thesurface of the molten reactant metal.

[0020]FIG. 4 is an isometric drawing of a preferred tire carrierstructure.

[0021]FIG. 5 is a somewhat diagrammatic isometric drawing of a preferredtire carrier, carrier lift structure, and cooling arrangement embodyingthe principles of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022]FIG. 1 illustrates major portions of a tire processing apparatus10 embodying the principles of the invention. Apparatus 10 includes areactor vessel 11 and a heater/circulating arrangement 12. Apparatus 10also includes a gas recovery arrangement shown generally at referencenumeral 14. Gas recovery arrangement 14 includes gas recovery hood 15,purge gas supply 16, aqueous scrubber 17, and solids separator 18.

[0023] Referring to FIG. 2, reactor vessel 11 is charged with a suitablereactant metal 19. The reactant metal preferably includes primarilyaluminum and may include minor amounts of iron, copper, zinc, andcalcium. A suitable reactant alloy is disclosed in U.S. Pat. No.5,000,101, which is incorporated herein by this reference. Although notshown in the drawings, a layer of graphite may be positioned on thesurface of the reactant metal 19 to help the molten metal retain heatand reduce oxide formation at the surface of the metal.

[0024] The heater 12 shown in FIG. 1 comprises a suitable heating systemfor heating the reactant metal to a molten state which may preferably befrom approximately 850° to 950° Celsius. The circulating systemassociated with heater 12 circulates fresh reactant metal into reactorvessel 11 and helps maintain the reactant metal in the vessel at thedesired temperature. The heater may be gas fired or, alternatively,comprise an electrical induction heating system. Details of the heaterand circulating system 12 are omitted from this disclosure so as not toobscure the invention in unnecessary detail. In any event, the heaterand reactant metal circulating system 12 is within the knowledge ofthose skilled in this art.

[0025] Referring still to FIG. 2, apparatus 10 also includes a tirepositioning arrangement shown generally at reference numeral 20. Thetire positioning arrangement 20 includes a tire carrier 21 and carrierlift structure 22, as well as a tire contactor member 23 and at leastone contactor actuator 24. Although the illustrated form of theinvention includes two contactor actuators, other arrangements mayinclude one or more contactor actuators.

[0026] Tire carrier 21 and carrier lift structure 22 are described inmore detail with reference to FIGS. 4 and 5 below. However, as shown inFIG. 2, tire carrier 21 includes a structure on which whole tires 26 tobe processed may be loaded. Carrier lift structure 22 moves the tirecarrier 21 from a loading/collecting position described below,particularly with reference to FIG. 5, to a reaction position shown inFIG. 2. In the reaction position, the tire carrier 21 is below thesurface of the reactant metal far enough to allow tires 26 loaded on thecarrier to be fully submerged in the reactant metal 19.

[0027] Tire contactor member 23 and contactor actuators 24 help ensurethat the tires 26 to be processed are fully submerged in the reactantmetal 19. As a tire carrier 21 loaded with tires 26 descends into thereactant metal 19, tires may tend to float on the surface of thereactant metal. Contactor member 23 above the tire carrier 21 movesdownwardly on its actuators 24 to press the tires 26 into the moltenreactant metal 19. The illustrated contactor member 23 and contactoractuators 24 are conveniently associated with the gas recovery hood 15.However, the contactor member 23 and contactor actuators 24 need not beassociated with the hood 15. Also, the contactor actuators 24 maycomprise any suitable actuators, including hydraulic actuators ormechanical actuators, for example.

[0028] As shown in FIG. 2, gas recovery hood 15 is suspended on hoodsupports 30 which are connected to hood actuators 31. Hood actuators 31operate to move hood 15 up and down along axis H. Gas recovery hood 15is shown in an operating position in FIG. 2 and may be raised byactuators 31 to a retracted position well above the reactor vessel 11.The hood actuators 31, hood supports 30, and gas recovery hood 15 areall supported on a superstructure 32. As with the contactor actuators24, hood actuators 31 may comprise any suitable actuators such ashydraulic or mechanical actuators, for example. Although three separatehood actuators 31 are shown for purposes of example in FIG. 2, one ormore hood actuators may be used within the scope of the invention. Amoveable purge gas conduit 33 is connected to the hood 15 at one end anda moveable outlet conduit 34 is connected at the opposite end of the gasrecovery hood. Purge gas conduit 33 extends to the purge gas supplyshown in FIG. 1, while outlet conduit 34 extends to the aqueous scrubber17 also shown in FIG. 1. Both the conduits 33 and 34 must be capable ofmoving to accommodate the movement of the gas recovery hood 15 betweenits operating position and retracted position.

[0029] Reactor vessel 11, tire carrier 21, tire contactor member 23,portions of the gas recovery hood 15, and all other elements which comeinto contact with the molten reactant metal 19 may comprise any suitablemetal which retains sufficient strength at the high operatingtemperatures of the reactant metal. All of these elements are preferablycoated with a ceramic or refractory material which protects theunderlying structural metal from degradation by contact with thereactant metal 19 in the reactor vessel 11.

[0030] The operation of the tire processing apparatus 10 may bedescribed with reference to FIGS. 3A, 3B, and 3C. FIG. 3A shows the gasrecovery hood 15 in its retracted position and a tire carrier 21 loadedwith tires 26 to be processed in a ready position in which it residesjust above the surface of the molten reactant metal 19. As shown in FIG.3B, the tire treating method includes lowering gas recovery hood 15 toan operating position. In the operating position, the lower edge of thegas recovery hood 15 extends into the reactant metal 19 around theentire periphery of tire carrier 21, that is, around the area in whichtires 26 are to be submerged. At this point, the gas recovery hood 15defines a gas collection area 38 over the area in which tires are to besubmerged. Once hood 15 is in the operating position, the preferred tiretreatment method includes purging the gas collection area 38 of air witha suitable purge gas such as nitrogen, for example, supplied from purgegas supply 16 shown in FIG. 1. Purging the gas collection area 38 of airhelps prevent the production of CO₂ which would have to be released intothe atmosphere. Although it is possible to operate the apparatus 10without purging the gas collection area 38, it is desirable to reduceCO₂ emissions and thus, purging the gas collection area is preferred.

[0031] As shown in FIG. 3C, after gas recovery hood 15 is placed in theoperating position and any purge operation is complete, the tire carrier21 and tires 26 to be processed are lowered into the reactant metal 19.The tire contactor member 23 also moves downwardly to a second positionin which it presses the tires 26 below the surface of the reactantmetal.

[0032] The tire treatment method includes holding the tires 26 in thereaction position contacting the reactant metal 19 for a reaction periodwhich will depend upon the number of tires being processed. The reactionperiod is a period of time sufficient to react substantially allmaterial included in the tires except for any stainless steel which maybe included in the tire carcass. The stainless steel in the tires doesnot react chemically with the reactant metal 19, but will dissolve intothe reactant metal over time. Thus, once the organic compounds in thetires are reacted with the molten reactant metal 19, the carrier liftstructure 20 shown in FIG. 2 lifts the tire carrier 21 and unreactedsolids out of the reactant metal, once again to the position shown inFIG. 3B. At this point, the gas collection area 38 under gas recoveryhood 15 is preferably again purged with a suitable inert gas to move allprocess gases out through outlet conduit 34 to scrubber 17. Afterpurging the gas collection area 38, the hood 15 is raised to the fullyretracted position and the tire carrier 21, now carrying the unreactedsolids comprising primarily stainless steel, is raised completely out ofthe reactor vessel 11 so that the carrier may be moved to itsloading/collection position discussed below with reference to FIG. 5.

[0033] Tires are comprised of approximately 56% various organiccompounds, including rubber and natural and synthetic binders, 30%carbon black, 10% stainless steel, and 4% inert materials by weight. Thepreferred molten aluminum or aluminum alloy reactant metal stripselements from the carbon atoms in the organic compounds to form variousaluminum and perhaps other metal salts. The liberated carbon sublimes toa gaseous state at the operating temperature of the molten reactantmetal and some of the metal salts may also go into a gaseous phase.Other metal salts produced by the reaction may separate by gravity tothe top of the reactant metal alloy below any graphite layer.

[0034] All of the process gases, including gaseous carbon, metal salts,hydrogen, and perhaps nitrogen release from the reactant metal andcollect in the gas collection area 38 under gas recovery hood 15. Thecollected process gases then flow through outlet conduit 34 to thematerial recovery system which preferably includes the aqueous scrubber17 and solids separator 18 shown in FIG. 1. Water in the aqueousscrubber 17 cool the carbon in the process gases to form fine carbonparticles in the scrubber effluent. Metal salts in the process gases arealso cooled in the scrubber 17 and go into solution in the scrubbereffluent. The scrubber effluent is directed to solids separator 18 whichseparates the carbon from the aqueous metal salt solution. The resultingcarbon may be formed into bricks which have a high fuel value. The metalsalts may be removed from the solution by any suitable process and theseparated water is preferably recycled back to the aqueous scrubber 17.

[0035]FIG. 4 shows a preferred tire carrier 21 loaded with wasted tires26 to be processed. Tire carrier 21 includes an open structure 44 whichallows reactant metal to flow easily around the tires 26 as the carrieris lowered into the molten reactant metal 19 shown in FIG. 2. The openstructure 44 also allows excess reactant metal to drain from the tirecarrier 21 as it is lifted out of the reactant metal after the reactionperiod. However, the open structure 44 of tire carrier 21 providessufficient support to hold unreacted solids, primarily stainless steel,and prevent the stainless steel from slipping into the reactant metal 19as the carrier is lifted out of the reactor vessel 11.

[0036]FIG. 5 shows a plurality of tire carriers 21 and a preferredcarrier lift structure 22. Each tire carrier 21 is connected to the liftstructure 22 through a goose neck or U-shaped support 47 which isrequired in order to allow gas recovery hood 15 to form the desired sealaround an individual tire carrier as shown in FIGS. 3B and 3C. A centrallift mechanism 48 of the carrier lift structure 22 is capable ofrotating in the direction R and also, is capable of moving along axis L.Thus, for example, the tire carrier 21 shown in the foreground in FIG. 5may be in the reaction position within the reactor vessel 11 (not shownin FIG. 5), while the other tire carriers 21 are each removed from thereactor vessel in a loading or collecting position. The tire carrier 21on the right in FIG. 5 may be in a collecting position in whichstainless steel left after reacting tires with the reactant metal may beremoved from the tire carrier. The tire carrier 21 on the left in FIG. 5may be in a loading position in which waste tires 26 are loaded forprocessing. In any event, cooling fans 50 or another suitable coolingarrangement may be associated with the apparatus 10 for cooling the tirecarriers 21 in the loading or collecting positions. After one of thetire carriers 21 is removed from the molten reactant metal 19 shown inFIG. 1, the cooling fans 50 cool the respective tire carrier down to atemperature at which unreacted solids may be conveniently removed fromthe carrier and additional tires may be loaded.

[0037] The above described preferred embodiments are intended toillustrate the principles of the invention, but not to limit the scopeof the invention. Various other embodiments and modifications to thesepreferred embodiments may be made by those skilled in the art withoutdeparting from the scope of the following claims. For example, althoughthe illustrated form of the invention shows linear actuators for movingthe gas recovery hood 15 and tire contactor member 23 along verticalaxes, alternate actuator arrangements may pivot the hood and tirecontactor member into and out of position. Also, although the inventionis suited to processing substantially whole tires, and thereforeeliminate a tire shredding step, whole tires may be cut up into smallerpieces prior to processing according to the invention. However, the tirecarrier must accommodate the smaller tire pieces without allowing piecesof stainless steel to fall into the molten reactant metal as the carrieris removed from the reactor vessel.

1. A method for recovering material from waste tires, the methodcomprising the steps of: (a) contacting substantially whole waste tireswith a molten reactant metal for a reaction period; (b) collectingprocess gases released from the molten reactant metal during thereaction period; (c) containing the waste tires on a tire carrier whenthe waste tires are contacted by the molten reactant metal; and (d)removing unreacted solids from the molten reactant metal after thereaction period, the unreacted solids being contained on the tirecarrier for removal.
 2. The method of claim 1 wherein the steps ofcontacting the waste tires with the molten reactant metal and containingthe waste tires on the tire carrier include: (a) lowering the wastetires into the molten reactant metal on the tire carrier; and (b)pressing the waste tires into the molten reactant metal with a tirecontactor member extending across an area above the tire carrier.
 3. Themethod of claim 2 wherein the step of removing unreacted solids from themolten reactant metal includes: (a) lifting the tire contactor memberand the tire carrier from the molten reactant metal and allowing themolten reactant metal to drain from around the unreacted solids, tirecontactor member, and tire carrier; and (b) cooling the tire carrier andunreacted solids located on the tire carrier.
 4. The method of claim 3wherein the step of cooling the tire carrier and unreacted solids on thetire carrier comprises: (a) moving the tire carrier to a cooling areaand forcing air over the tire carrier and unreacted solids located onthe tire carrier.
 5. The method of claim 1 wherein the step ofcollecting process gases comprises: (a) positioning a gas recovery hoodin an operating position in which a lower edge thereof extends into themolten reactant metal around the area in which the waste tires are tocontact the molten reactant metal, the gas recovery hood defining a gascollection area in which the process gases released from the moltenreactant metal are trapped.
 6. The method of claim 5 further comprisingthe step of: (a) directing process gases trapped in the gas collectionarea to an aqueous scrubber and removing metal salts and carbon from theprocess gas with the aqueous scrubber.
 7. The method of claim 5 furthercomprising the step of: (a) purging the gas collection area of air priorto collecting substantial amounts of process gases in the gas collectionarea.